Assessment of Bmi-1 on Protein and Molecular Levels in Oral Dysplasia and Squamous Cell Carcinoma: A Diagnostic Study

Head and neck squamous cell carcinoma (HNSCC) including oral squamous cell carcinoma (OSCC) has been reported as the sixth most common cause of cancer mortality in the world and the fifth most commonly occurring cancer. Thus a compelling need for investigation of the underlying molecular events associated with OSCC tumorigenesis has emerged for better understanding of such lesion. Moreover, identification of biomarkers for early detection and prediction of prognosis became of extreme importance, as it was reported that early diagnosis has been vital for effective treatment of OSCC and improved the survival rate of OSCC patients. OSCC may originate from malignant transformation of the normal oral mucosa, as well as from oral potentially malignant lesions (OPMLs) with different degrees of oral epithelial dysplasia (OED). The approach of a step-wise transition from OPMLs to OSCC was well-established, but it could be difficult to predict if and when an OPML would undergo full transformation and resulted in a tumor. Thus, using specific molecular biomarkers able to identify OED lesions with higher potential for malignant transformation would be very beneficial. Unfortunately, up to date there has been no tools available to monitor OED lesions or HNSCC patients for early stages of local recurrences or distant metastases . Among the recently introduced biomarkers, B-lymphoma Moloney murine leukemia virus insertion region-1 (BMI1), a member of the polycomb group (PcG) genes, was considered to be pivotal in regulating stemness-related genes involved in maintaining the self-renewal ability of stem cells by promoting chromatin modifications. BMI1 was also known to be deregulated in various human types of cancer. Previous studies have revealed the capability of BMI1 to be used as a prognostic marker in gastric, esophageal, nasopharyngeal cancer, prostate, breast, cervical and ovarian cancer, However, the role of BMI1 in maintaining self-renewal and tumorigenicity in HNSCC or HNSCC-derived cancer stem cells (CSCs) remained to be clarified.